Corrosion inhibitors for fuels and lubricants

ABSTRACT

The present invention relates to novel uses of corrosion inhibitors in fuels and lubricants.

The present invention relates to novel uses of corrosion inhibitors infuels and lubricants. Corrosion inhibitors are standard additives infuels and lubricants, which are often based on

structures containing acid groups, for example dimer fatty acids.

A disadvantage of these corrosion inhibitors is that they have atendency to precipitate, especially in the presence of calcium ions, asa result of which their corrosion-inhibiting action is reduced. Thedeposits formed as a result of this precipitation can additionallyimpair the working of engines, engine constituents or parts of the fuelsystem, especially the injection system, specifically the injectionpumps or nozzles.

The “injection system” is understood to mean the part of the fuel systemin motor vehicles from the fuel pump up to and including the injectoroutlet. “Fuel system” is understood to mean the components of motorvehicles that are in contact with the particular fuel, preferably theregion from the tank up to and including the injector outlet.

In one embodiment of the present invention, the inventive compoundscounteract deposits not just in the injection system but also in therest of the fuel system, here especially deposits in fuel filters andpumps.

The problem addressed was therefore that of providing corrosioninhibitors which exhibit elevated compatibility with respect to calciumions and at the same time maintain their effect as a corrosioninhibitor.

The problem is solved by the use according to the claims.

U.S. Pat. No. 3,382,056 teaches the use of low molecular weightcopolymers comprising olefins and succinic acid and derivatives thereofin copolymerized form as anti-rust additives in refined fuelcompositions.

JP 55-085679 teaches the use of hydrolytically opened copolymers ofmolar mass Mw from 2000 to 30 000 from α-olefins having 20 to 60 carbonatoms and maleic anhydride as oil-soluble rust inhibitors in mineral oilor lubricants.

U.S. Pat. No. 5,080,686 and EP 299120 disclose that alkyl- andalkenylsuccinic acids and derivatives thereof and copolymers comprisingolefins and succinic acid and derivatives thereof in copolymerized formfunction as corrosion inhibitors in oxygenated fuel systems.

It is not apparent from any of these documents that the corrosioninhibitors of the invention have elevated compatibility with respect tocalcium ions.

U.S. Pat. No. 5,766,273 discloses using polymer mixtures comprisingcopolymers of maleic anhydride and α-olefins as one component asadditives for mineral oil distillates for improving the flow properties,especially the cloud point (CP) and the cold filter plugging point(CFPP). There are no pointers to use as a corrosion inhibitor.

WO 201111153178 discloses binding aromatic amines to copolymerscontaining carboxylic acid groups, the amides thus obtained functioningas lubricity additives. No anticorrosive effect of the copolymercontaining carboxylic acid groups is described.

WO 96/28486 discloses copolymers formed from monoethylenicallyunsaturated C4- to C12-dicarboxylic acids or anhydrides thereof with1-olefins having 3 to 14 carbon atoms.

The reaction thereof with amines leads to corrosion inhibitors; there isno description of any anticorrosive effect of the copolymer alone.

U.S. Pat. No. 5,670,462 describes copolymers of maleic anhydride and C₄to C₃₀ olefins. There is no description of use to counteract corrosion.

JP 2007-077216 describes oils comprising partial esters of copolymers ofmaleic anhydride and α-olefins with alkylene glycols. There is nodescription of any anticorrosive effect of the copolymer alone.

International patent application PCT/EP2015/051752, filed Jan. 29, 2015,discloses use of partly or fully hydrolyzed copolymers of maleicanhydride and α-olefins as corrosion inhibitors. The hydrolysis level inthis case has to be at least 10%.

Accordingly, the invention provides the use of copolymers obtainable by

-   -   in a first reaction step (I) copolymerizing

-   (A) at least one ethylenically unsaturated mono- or dicarboxylic    acid or derivatives thereof, preferably a dicarboxylic acid or    derivatives thereof, more preferably the anhydride of a dicarboxylic    acid,

-   (B) at least one α-olefin having from at least 12 up to and    including 30 carbon atoms,

-   (C) optionally at least one further aliphatic or cycloaliphatic    olefin which has at least 4 carbon atoms and is different than (B)    and

-   (D) optionally one or more further copolymerizable monomers other    than monomers (A), (B) and (C), selected from the group consisting    of

-   (Da) vinyl esters,

-   (Db) vinyl ethers,

-   (Dc) (meth)acrylic esters of alcohols having at least 5 carbon    atoms,

-   (Dd) allyl alcohols or ethers thereof,

-   (De) N-vinyl compounds selected from the group consisting of vinyl    compounds of heterocycles containing at least one nitrogen atom,    N-vinylamides or N-vinyllactams,

-   (Df) ethylenically unsaturated aromatics,

-   (Dg) α,β-ethylenically unsaturated nitriles,

-   (Dh) (meth)acrylamides and

-   (Di) allylamines,    followed by    -   in a second optional reaction step (II) partly hydrolyzing the        anhydride functionalities present in the copolymer obtained        from (I) and/or partly hydrolyzing carboxylic ester        functionalities present in the copolymer obtained from (I), with        the proviso that more than 90% of the anhydride and carboxylic        ester functionalities present remain intact after reaction step        (II), as corrosion inhibitors in fuels and lubricants,        preferably in fuels, more preferably in fuels having a content        of alkali metals and/or alkaline earth metals and/or zinc of at        least 0.1 ppm by weight.

The copolymers described are found to be particularly advantageous infuels or lubricants, particularly in fuels having a content of alkalimetals and/or alkaline earth metals and/or

zinc of at least 0.1 ppm by weight, more preferably at least 0.2 ppm byweight and even more preferably at least 0.3 ppm by weight andespecially at least 0.5 ppm by weight. Also conceivable is a content ofalkali metals and/or alkaline earth metals and/or zinc of at least 1 ppmby weight, preferably at least 2 and more preferably at least 3 ppm byweight.

It is an advantage of the copolymers described that they also exhibittheir corrosion-inhibiting action in the presence of alkali metalsand/or alkaline earth metals and/or zinc, preferably also in thepresence of alkaline earth metals. The content of alkali metals and/oralkaline earth metals in fuels results, for example, from mixing withlubricants containing alkali metals and/or alkaline earth metals, forexample in the fuel pump. In addition, alkali metals and/or alkalineearth metals may originate from non-desalinated or inadequatelydesalinated fuel additives, for example carrier oils. The entrainment ofalkali metals and/or alkaline earth metals into the fuels can cause theabovementioned disadvantages. One example of a zinc source is antiwearadditives.

Alkali metals include particularly sodium and potassium, especiallysodium.

Alkaline earth metals include particularly magnesium and calcium,especially calcium.

Zinc should also be emphasized.

Particularly advantageously, the reaction products described are stillactive even in the presence of calcium and do not exhibit anyprecipitation.

The stated amounts of alkali metals and/or alkaline earth metals and/orzinc each relate to individual metal species.

Description of the Copolymer

The monomer (A) is at least one, preferably one to three, morepreferably one or two and most preferably exactly one ethylenicallyunsaturated, preferably α,β-ethylenically unsaturated, mono- ordicarboxylic acid(s) or derivatives thereof, preferably a dicarboxylicacid or derivatives thereof.

Derivatives are understood to mean

-   -   the corresponding anhydrides in monomeric or else polymeric        form,    -   mono- or dialkyl esters, preferably mono- or di-C₁-C₄-alkyl        esters, more preferably mono- or dimethyl esters or the        corresponding mono- or diethyl esters, and    -   mixed esters, preferably mixed esters having different C₁-C₄        alkyl components, more preferably mixed methyl ethyl esters.

Preferably, the derivatives are anhydrides in monomeric form ordi-C₁-C₄-alkyl esters, more preferably anhydrides in monomeric form.

In the context of this document, C₁-C₄-alkyl is understood to meanmethyl, ethyl, iso-propyl, n-propyl, n-butyl, iso-butyl, sec-butyl andtert-butyl, preferably methyl and ethyl, more preferably methyl.

Examples of α,β-ethylenically unsaturated mono- or dicarboxylic acidsare those mono- or dicarboxylic acids or derivatives thereof in whichthe carboxyl group or, in the case of dicarboxylic acids, at least onecarboxyl group, preferably both carboxyl groups, is/are conjugated tothe ethylenically unsaturated double bond.

Examples of ethylenically unsaturated mono- or dicarboxylic acids thatare not α,β-ethylenically unsaturated arecis-5-norbornene-endo-2,3-dicarboxylic anhydride,exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride andcis-4-cyclohexene-1,2-dicarboxylic anhydride.

Examples of α,β-ethylenically unsaturated monocarboxylic acids areacrylic acid, methacrylic acid, crotonic acid and ethylacrylic acid,preferably acrylic acid and methacrylic acid, referred to in thisdocument as (meth)acrylic acid for short, and more preferably acrylicacid.

Particularly preferred derivatives of α,β-ethylenically unsaturatedmonocarboxylic acids are methyl acrylate, ethyl acrylate, n-butylacrylate and methyl methacrylate.

Examples of dicarboxylic acids are maleic acid, fumaric acid, itaconicacid (2-methylenebutanedioic acid), citraconic acid (2-methylmaleicacid), glutaconic acid (pent-2-ene-1,5-dicarboxylic acid),2,3-dimethylmaleic acid, 2-methylfumaric acid, 2,3-dimethylfumaric acid,methylenemalonic acid and tetrahydrophthalic acid, preferably maleicacid and fumaric acid and more preferably maleic acid and derivativesthereof.

More particularly, monomer (A) is maleic anhydride.

Monomer (B) is at least one, preferably one to four, more preferably oneto three, even more preferably one or two and most preferably exactlyone α-olefin(s) having from at least 12 up to and including 30 carbonatoms. The α-olefins (B) preferably have at least 14, more preferably atleast 16 and most preferably at least 18 carbon atoms. Preferably, theα-olefins (B) have up to and including 28, more preferably up to andincluding 26 and most preferably up to and including 24 carbon atoms.

Preferably, the α-olefins may be linear or branched, preferably linear,1-alkenes.

Examples of these are 1-dodecene, 1-tridecene, 1-tetradecene,1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonodecene,1-eicosene, 1-docosene, 1-tetracosene, 1-hexacosene, preference beinggiven to 1-octadecene, 1-eicosene, 1-docosene and 1-tetracosene, andmixtures thereof.

Further examples of α-olefin (B) are those olefins which are oligomersor polymers of C₂ to C₁₂ olefins, preferably of C₃ to C₁₀ olefins, morepreferably of C₄ to C₆ olefins. Examples thereof are ethene, propene,1-butene, 2-butene, isobutene, pentene isomers and hexene isomers,preference being given to ethene, propene, 1-butene, 2-butene andisobutene.

Named examples of α-olefins (B) include oligomers and polymers ofpropene, 1-butene, 2-butene, isobutene, and mixtures thereof,particularly oligomers and polymers of propene or Isobutene or ofmixtures of 1-butene and 2-butene. Among the oligomers, preference isgiven to the trimers, tetramers, pentamers and hexamers, and mixturesthereof.

In addition to the olefin (B), it is optionally possible to incorporateat least one, preferably one to four, more preferably one to three, evenmore preferably one or two and especially exactly one further aliphaticor cycloaliphatic olefin(s) (C) which has/have at least 4 carbon atomsand is/are different than (B) by polymerization into the inventivecopolymer.

The olefins (C) may be olefins having a terminal (α-)double bond orthose having a non-terminal double bond, preferably having an α-doublebond. The olefin (C) preferably comprises olefins having 4 to fewer than12 or more than 30 carbon atoms. If the olefin (C) is an olefin having12 to 30 carbon atoms, this olefin (C) does not have an α-double bond.

Examples of aliphatic olefins (C) are 1-butene, 2-butene, isobutene,pentene isomers, hexene isomers, heptene isomers, octene isomers, noneneisomers, decene isomers, undecene isomers and mixtures thereof.

Examples of cycloaliphatic olefins (C) are cyclopentene, cydohexene,cyclooctene, cydodecene, cyclododecene, α- or β-pinene and mixturesthereof, limonene and norbornene.

Further examples of olefins (C) are polymers having more than 30 carbonatoms of propene, 1-butene, 2-butene or isobutene or of olefin mixturescomprising the latter, preferably of isobutene or of olefin mixturescomprising the latter, more preferably having a mean molecular weightM_(w) in the range from 500 to 5000 g/mol, preferably 650 to 3000 andmore preferably 800 to 1500 g/mol.

Preferably, the oligomers or polymers comprising isobutene incopolymerized form have a high content of terminal ethylenic doublebonds (α-double bonds), for example at least 50 mol %, preferably atleast 60 mol %, more preferably at least 70 mol % and most preferably atleast 80 mol %.

For the preparation of such oligomers or polymers comprising isobutenein copolymerized form, suitable isobutene sources are either pureisobutene or isobutene-containing C4 hydrocarbon streams, for example C4raffinates, especially “raffinate 1”, C4 cuts from isobutanedehydrogenation, C4 cuts from steamcrackers and from FCC crackers (fluidcatalyzed cracking), provided that they have substantially been freed of1,3-butadiene present therein. A C4 hydrocarbon stream from an FCCrefinery unit is also known as a “b/b” stream. Further suitableisobutene-containing C4 hydrocarbon streams are, for example, theproduct stream of a propylene-isobutane cooxidation or the productstream from a metathesis unit, which are generally used after customarypurification and/or concentration. Suitable C4 hydrocarbon streamscomprise generally less than 500 ppm, preferably less than 200 ppm, ofbutadiene. The presence of 1-butene and of cis- and trans-2-butene issubstantially uncritical. Typically, the isobutene concentration in saidC4 hydrocarbon streams is in the range from 40% to 60% by weight. Forinstance, raffinate 1 generally consists essentially of 30% to 50% byweight of isobutene, 10% to 50% by weight of 1-butene, 10% to 40% byweight of cis- and trans-2-butene and 2% to 35% by weight of butanes; inthe polymerization process of the invention, the unbranched butenes inthe raffinate 1 are generally virtually inert, and only the isobutene ispolymerized.

In a preferred embodiment, the monomer source used for polymerization isa technical C4 hydrocarbon stream having an isobutene content of 1% to100% by weight, especially of 1% to 99% by weight, in particular of 1%to 90% by weight, more preferably of 30% to 60% by weight, especially araffinate 1 stream, a b/b stream from an FCC refinery unit, a productstream from a propylene-isobutane cooxidation or a product stream from ametathesis unit.

Especially when a raffinate 1 stream is used as isobutene source, theuse of water as the sole initiator or as further initiator has beenfound to be useful, particularly when polymerization is effected attemperatures of −20° C. to +30° C., especially of 0° C. to +20° C. Attemperatures of −20° C. to +30° C., especially of 0° C. to +20° C.however, it is possible to dispense with the use of an initiator whenusing a raffinate 1 stream as isobutene source.

Said isobutene-containing monomer mixture may comprise small amounts ofcontaminants such as water, carboxylic acids or mineral acids withoutcausing any critical yield or selectivity losses. It is appropriate tothe purpose to avoid accumulation of these impurities by removing suchharmful substances from the isobutene-containing monomer mixture, forexample, by adsorption on solid adsorbents such as activated carbon,molecular sieves or ion exchangers.

It is also possible, albeit less preferable, to convert monomer mixturesof isobutene or of the isobutene-containing hydrocarbon mixture witholefinically unsaturated monomers copolymerizable with isobutene. Ifmonomer mixtures of isobutene with suitable comonomers are to becopolymerized, the monomer mixture comprises preferably at least 5% byweight, more preferably at least 10% by weight and especially at least20% by weight of isobutene, and preferably at most 95% by weight, morepreferably at most 90% by weight and especially at most 80% by weight ofcomonomers.

In a preferred embodiment, the mixture of the olefins (B) and optionally(C), averaged to their molar amounts, have at least 12 carbon atoms,preferably at least 14, more preferably at least 16 and most preferablyat least 17 carbon atoms.

For example, a 2:3 mixture of docosene and tetradecene has an averagedvalue for the carbon atoms of 0.4×22+0.6×14=17.2.

The upper limit is less relevant and is generally not more than 60carbon atoms, preferably not more than 55, more preferably not more than50, even more preferably not more than 45 and especially not more than40 carbon atoms.

The optional monomer (D) is at least one monomer, preferably one tothree, more preferably one or two and most preferably exactly onemonomer(s) selected from the group consisting of

-   (Da) vinyl esters,-   (Db) vinyl ethers,-   (Dc) (meth)acrylic esters of alcohols having at least 5 carbon    atoms,-   (Dd) allyl alcohols or ethers thereof,-   (De) N-vinyl compounds selected from the group consisting of vinyl    compounds of heterocycles containing at least one nitrogen atom,    N-vinylamides or N-vinyllactams,-   (Df) ethylenically unsaturated aromatics and-   (Dg) α,β-ethylenically unsaturated nitriles,-   (Dh) (meth)acrylamides and-   (Di) allylamines.

Examples of vinyl esters (Da) are vinyl esters of C₂- to C₁₂-carboxylicacids, preferably vinyl acetate, vinyl propionate, vinyl butyrate, vinylpentanoate, vinyl hexanoate, vinyl octanoate, vinyl 2-ethylhexanoate,vinyl decanoate, and vinyl esters of Versatic Acids 5 to 10, preferablyvinyl esters of 2,2-dimethylpropionic acid (pivalic acid, Versatic Acid5), 2,2-dimethylbutyric acid (neohexanoic acid, Versatic Acid 6),2,2-dimethylpentanoic acid (neoheptanoic acid, Versatic Acid 7),22-dimethylhexanoic acid (neooctanoic acid, Versatic Acid 8),2,2-dimethylheptanolc acid (neononanoic acid, Versatic Acid 9) or2,2-dimethyloctanoic acid (neodecanoic acid, Versatic Acid 10).

Examples of vinyl ethers (Db) are vinyl ethers of C₁- to C₁₂-alkanols,preferably vinyl ethers of methanol, ethanol, iso-propanol, n-propanol,n-butano, iso-butanol, sec-butanol, tert-butanol, n-hexanol, n-heptanol,n-octanol, n-decanol, n-dodecanol (lauryl alcohol) or 2-ethylhexanol.

Preferred (meth)acrylic esters (Dc) are (meth)acrylic esters of C₅- toC₁₂-alkanols, preferably of n-pentanol, n-hexanol, n-heptanol,n-octanol, n-decanol, n-dodecanol (lauryl alcohol), 2-ethylhexanol or2-propylheptanol. Particular preference is given to pentyl acrylate,2-ethylhexyl acrylate, 2-propylheptyl acrylate.

Examples of monomers (Dd) are allyl alcohols and allyl ethers of C₂- toC₁₂-alkanols, preferably allyl ethers of methanol, ethanol,iso-propanol, n-propanol, n-butanol, iso-butanol, sec-butanol,tert-butanol, n-hexanol, n-heptanol, n-octanol, n-decanol, n-dodecanol(lauryl alcohol) or 2-ethylhexanol.

Examples of vinyl compounds (De) of heterocycles comprising at least onenitrogen atom are N-vinylpyridine, N-vinylimidazole andN-vinylmorpholine.

Preferred compounds (De) are N-vinylamides or N-vinyllactams.

Examples of N-vinylamides or N-vinyllactams (De) are N-vinylformamide,N-vinylacetamide, N-vinylpyrrolidone and N-vinylcaprolactam.

Examples of ethylenically unsaturated aromatics (Df) are styrene andα-methylstyrene.

Examples of α,β-ethylenically unsaturated nitriles (Dg) areacrylonitrile and methacrylonitrile.

Examples of (meth)acrylamides (Dh) are acrylamide and methacrylamide.

Examples of allylamines (Di) are allylamine, dialkylallylamine andtrialkylallylammonium halides.

Preferred monomers (D) are (Da), (Db), (Dc), (De) and/or (Df), morepreferably (Da), (Db) and/or (Dc), even more preferably (Da) and/or (Dc)and especially (Dc).

The incorporation ratio of the monomers (A) and (B) and optionally (C)and optionally (D) in the polymer obtained from reaction step (I) isgenerally as follows: The molar ratio of (A)/((B) and (C)) (in total) isgenerally from 10:1 to 1:10, preferably 8:1 to 1:8, more preferably 5:1to 1:5, even more preferably 3:1 to 1:3, particularly 2:1 to 1:2 andespecially 1.5:1 to 1:1.5. In the particular case of maleic anhydride asmonomer (A), the molar incorporation ratio of maleic anhydride tomonomers ((B) and (C)) (in total) is about 1:1. In order to achievecomplete conversion of the α-olefin (B), it may nevertheless beadvisable to use maleic anhydride in a slight excess over the α-olefin,for example 1.01-1.5:1, preferably 1.02-1.4:1, more preferably1.05-1.3:1, even more preferably 1.07-1.2:1 and especially 1.1-1.15:1.

The molar ratio of obligatory monomer (B) to monomer (C), if present, isgenerally of 1:0.05 to 10, preferably of 1:0.1 to 6, more preferably of1:0.2 to 4, even more preferably of 1:0.3 to 2.5 and especially 1:0.5 to1.5.

In a preferred embodiment, no optional monomer (C) is present inaddition to monomer (B).

The proportion of one or more of the monomers (D), if present, based onthe amount of the monomers (A), (B) and optionally (C) (in total) isgenerally 5 to 200 mol %, preferably 10 to 150 mol %, more preferably 15to 100 mol %, even more preferably 20 to 50 mol % and especially 0 to 25mol %.

In a preferred embodiment, no optional monomer (D) is present.

In a particularly preferred embodiment, the copolymer consists ofmonomers (A) and (B).

In a second optional reaction step (II), the anhydride or carboxylicester functionalities present in the copolymer obtained from (1) may bepartly hydrolyzed and/or saponified. Preferably, in reaction step (11),anhydride functionalities are hydrolyzed and carboxylic esterfunctionalities are left essentially intact.

According to the invention, more than 90% of the anhydride andcarboxylic ester functionalities present remain intact after reactionstep (II), preferably at least 92%, more preferably at least 94%, evenmore preferably at least 95%, particularly at least 97% and especiallyat least 98%.

It is possible that up to 99.9% of the anhydride and carboxylic esterfunctionalities present remain intact after reaction step (II),preferably up to 99.8%, more preferably up to 99.7%, even morepreferably up to 99.5% and especially up to 99%.

In a preferred embodiment, reaction step (II) is not conducted, and so100% of the anhydride and carboxylic ester functionalities present inthe copolymer obtained from reaction step (I) remain intact.

A hydrolysis in reaction step (II) is conducted when the derivative ofmonomer (A) used is an anhydride, preferably the anhydride of adicarboxylic acid, whereas a saponification or hydrolysis can beconducted when an ester is used as monomer (A).

For a hydrolysis, based on the anhydride functionalities present, theamount of water that corresponds to the desired hydrolysis level isadded and the copolymer obtained from (I) is heated in the presence ofthe added water. In general, a temperature of preferably 20 to 150° C.is sufficient for the purpose, preferably 60 to 100° C. If required, thereaction can be conducted under pressure in order to prevent the escapeof water. Under these reaction conditions, in general, the anhydridefunctionalities in the copolymer are converted selectively, whereas anycarboxylic ester functionalities present in the copolymer react at leastonly to a minor degree, if at all.

For a saponification, the copolymer is reacted with an amount of astrong base corresponding to the desired saponification level in thepresence of water.

Strong bases used may preferably be hydroxides, oxides, carbonates orhydrogencarbonates of alkali metals or alkaline earth metals.

The copolymer obtained from (I) is then heated in the presence of theadded water and the strong base. In general, a temperature of preferably20 to 130° C. is sufficient for the purpose, preferably 50 to 110° C. Ifrequired, the reaction can be conducted under pressure.

It is also possible to hydrolyze the carboxylic ester functionalitieswith water in the presence of an acid. Acids used are preferably mineralacids, carboxylic acids, sulfonic acids or phosphorus acids having a pKaof not more than 5, more preferably not more than 4.

Examples are acetic acid, formic acid, oxalic acid, salicylic acid,substituted succinic acids, aromatically substituted or unsubstitutedbenzenesulfonic acids, sulfuric acid, nitric acid, hydrochloric acid orphosphoric acid; the use of acidic ion exchange resins is alsoconceivable.

The copolymer obtained from (I) is then heated in the presence of theadded water and the acid. In general, a temperature of preferably 40 to200° C. is sufficient for the purpose, preferably 80 to 150° C. Ifrequired, the reaction can be conducted under pressure.

Should the copolymers obtained from step (II) still comprise residues ofacid anions, it may be preferable to remove these acid anions from thecopolymer with the aid of an ion exchanger and preferably exchange themfor hydroxide ions or carboxylate ions, more preferably hydroxide ions.This is the case especially when the acid anions present in thecopolymer are halides or contain sulfur or nitrogen.

The copolymer obtained from reaction step (II) generally has aweight-average molecular weight Mw of 0.5 to 20 kDa, preferably 0.6 to15, more preferably 0.7 to 7, even more preferably 1 to 7 and especially1.5 to 4 kDa (determined by gel permeation chromatography withtetrahydrofuran and polystyrene as standard).

The number-average molecular weight Mn is usually from 0.5 to 10 kDa,preferably 0.6 to 5, more preferably 0.7 to 4, even more preferably 0.8to 3 and especially 1 to 2 kDa (determined by gel permeationchromatography with tetrahydrofuran and polystyrene as standard).

The polydispersity is generally from 1 to 10, preferably from 1.1 to 8,more preferably from 1.2 to 7, even more preferably from 1.3 to 5 andespecially from 1.5 to 3.

The content of free acid groups in the copolymer after conductingreaction step (II) is preferably less than 5 mmol/g of copolymer, morepreferably less than 3, even more preferably less than 2 mmol/g ofcopolymer and especially less than 1 mmol/g of copolymer.

In a preferred embodiment, the copolymers comprise a high proportion ofadjacent carboxylic acid groups, which is determined by a measurement ofadjacency. For this purpose, a sample of the copolymer is heat-treatedbetween two Teflon films at a temperature of 290° C. for a period of 30minutes and an FTIR spectrum is recorded at a bubble-free site. The IRspectrum of Teflon is subtracted from the spectra obtained, the layerthickness is determined and the content of cyclic anhydride isdetermined.

In a preferred embodiment, the adjacency is at least 10%, preferably atleast 15%, more preferably at least 20%, even more preferably at least25% and especially at least 30%.

Use

The use of the invention relates to the inhibition of corrosion of ironsurfaces, steel surfaces and/or nonferrous metal surfaces.

Among the nonferrous metals, preference is given to copper and alloysthereof.

Particular preference is given to inhibiting the corrosion of steelsurfaces.

The copolymers described are added to fuels having the above-specifiedcontent of alkali metals and/or alkaline earth metals and/or zincgenerally in amounts of 1 to 60 and preferably 4 to 50 ppm by weight,and more preferably from 10 to 40 ppm by weight.

Frequently, the copolymers described are used in the form of fueladditive mixtures, together with customary additives:

In the case of diesel fuels, these are primarily customary detergentadditives, carrier oils, cold flow improvers, lubricity improvers,corrosion inhibitors other than the copolymers described, demulsifiers,dehazers, antifoams, cetane number improvers, combustion improvers,antioxidants or stabilizers, antistats, metallocenes, metaldeactivators, dyes and/or solvents.

In the case of gasoline fuels, these are in particular lubricityimprovers (friction modifiers), corrosion inhibitors other than thecopolymers described, demulsifiers, dehazers, antifoams, combustionimprovers, antioxidants or stabilizers, antistats, metallocenes, metaldeactivators, dyes and/or solvents.

Typical examples of suitable coadditives are listed in the followingsection:

B1) Detergent Additives

The customary detergent additives are preferably amphiphilic substanceswhich possess at least one hydrophobic hydrocarbon radical with anumber-average molecular weight (M_(n)) of 85 to 20 000 and at least onepolar moiety selected from:

-   (Da) mono- or polyamino groups having up to 6 nitrogen atoms, at    least one nitrogen atom having basic properties;-   (Db) nitro groups, optionally in combination with hydroxyl groups;-   (Dc) hydroxyl groups in combination with mono- or polyamino groups,    at least one nitrogen atom having basic properties;-   (Dd) carboxyl groups or the alkali metal or alkaline earth metal    salts thereof;-   (De) sulfonic acid groups or the alkali metal or alkaline earth    metal salts thereof;-   (Df) polyoxy-C₂- to C₄-alkylene moieties terminated by hydroxyl    groups, mono- or polyamino groups, at least one nitrogen atom having    basic properties, or by carbamate groups;-   (Dg) carboxylic ester groups:-   (Dh) moieties derived from succinic anhydride and having hydroxyl    and/or amino and/or amido and/or imido groups; and/or-   (Di) moieties obtained by Mannich reaction of substituted phenols    with aldehydes and mono- or polyamines.

The hydrophobic hydrocarbon radical in the above detergent additives,which ensures the adequate solubility in the fuel, has a number-averagemolecular weight (M_(n)) of 85 to 20 000, preferably of 113 to 10 000,more preferably of 300 to 5000, even more preferably of 300 to 3000,even more especially preferably of 500 to 2500 and especially of 700 to2500, in particular of 800 to 1500. As typical hydrophobic hydrocarbonradicals, especially in conjunction with the polar, especiallypolypropenyl, polybutenyl and polyisobutenyl radicals with anumber-average molecular weight M of preferably in each case 300 to5000, more preferably 300 to 3000, even more preferably 500 to 2500,even more especially preferably 700 to 2500 and especially 800 to 1500into consideration.

Examples of the above groups of detergent additives include thefollowing:

Additives comprising mono- or polyamino groups (Da) are preferablypolyalkenemono- or polyalkenepolyamines based on polypropene or onhigh-reactivity (i.e. having predominantly terminal double bonds) orconventional (i.e. having predominantly internal double bonds)polybutene or polyisobutene with M_(n)=300 to 5000, more preferably 500to 2500 and especially 700 to 2500. Such additives based onhigh-reactivity polyisobutene, which can be prepared from thepolyisobutene which may comprise up to 20% by weight of n-butene unitsby hydroformylation and reductive amination with ammonia, monoamines orpolyamines such as dimethylaminopropylamine, ethylenediamine,diethylenetriamine, triethylenetetramine or tetraethylenepentamine, areknown especially from EP-A 244 616. When polybutene or polyisobutenehaving predominantly internal double bonds (usually in the β and γpositions) are used as starting materials in the preparation of theadditives, a possible preparative route is by chlorination andsubsequent amination or by oxidation of the double bond with air orozone to give the carbonyl or carboxyl compound and subsequent aminationunder reductive (hydrogenating) conditions. The amines used here for theamination may be, for example, ammonia, monoamines or the abovementionedpolyamines. Corresponding additives based on polypropene are describedmore particularly in WO-A 94/24231.

Further particular additives comprising monoamino groups (Da) are thehydrogenation products of the reaction products of polyisobutenes havingan average degree of polymerization P=5 to 100 with nitrogen oxides ormixtures of nitrogen oxides and oxygen, as described more particularlyin WO-A 97/03946.

Further particular additives comprising monoamino groups (Da) are thecompounds obtainable from polyisobutene epoxides by reaction with aminesand subsequent dehydration and reduction of the amino alcohols, asdescribed more particularly in DE-A 196 20 262.

Additives comprising nitro groups (Db), optionally in combination withhydroxyl groups, are preferably reaction products of polyisobuteneshaving an average degree of polymerization P=5 to 100 or 10 to 100 withnitrogen oxides or mixtures of nitrogen oxides and oxygen, as describedmore particularly in WO-A 96/03367 and in WO-A 96/03479. These reactionproducts are generally mixtures of pure nitropolyisobutenes (e.g.α,β-dinitropolyisobutene) and mixed hydroxynitropolyisobutenes (e.g.α-nitro-β-hydroxypolyisobutene).

Additives comprising hydroxyl groups in combination with mono- orpolyamino groups (Dc) are especially reaction products of polyisobuteneepoxides obtainable from polyisobutene having preferably predominantlyterminal double bonds and M_(n)=300 to 5000, with ammonia or mono- orpolyamines, as described more particularly in EP-A 476 485.

Additives comprising carboxyl groups or their alkali metal or alkalineearth metal salts (Dd) are preferably copolymers of C₂- to C₄₀-olefinswith maleic anhydride which have a total molar mass of 500 to 20 000 andwherein some or all of the carboxyl groups have been converted to thealkali metal or alkaline earth metal salts and any remainder of thecarboxyl groups has been reacted with alcohols or amines. Such additivesare disclosed more particularly by EP-A 307 815. Such additives servemainly to prevent valve seat wear and can, as described in WO-A87/01126, advantageously be used in combination with customary fueldetergents such as poly(iso)buteneamines or polyetheramines.

Additives comprising sulfonic acid groups or their alkali metal oralkaline earth metal salts (De) are preferably alkali metal or alkalineearth metal salts of an alkyl sulfosuccinate, as described moreparticularly in EP-A 639 632. Such additives serve mainly to preventvalve seat wear and can be used advantageously in combination withcustomary fuel detergents such as poly(iso)buteneamines orpolyetheramines.

Additives comprising polyoxy-C₂-C₄-alkylene moieties (Df) are preferablypolyethers or polyetheramines which are obtainable by reaction of C₂- toC₆₀-alkanols. C₆- to C₃₀-alkanediols, mono- or di-C₂ to C₃₀-alkylamines,C₁- to C₃₀-alkylcyclohexanols or C₁- to C₃₀-alkylphenols with 1 to 30mol of ethylene oxide and/or propylene oxide and/or butylene oxide perhydroxyl group or amino group and, in the case of the polyetheramines,by subsequent reductive amination with ammonia, monoamines orpolyamines. Such products are described more particularly in EP-A 310875, EP-A 356 725, EP-A 700 985 and U.S. Pat. No. 4,877,416. In the caseof polyethers, such products also have carrier oil properties. Typicalexamples thereof are tridecanol butoxylates or isotridecanolbutoxylates, isononylphenol butoxylates and also polyisobutenolbutoxylates and propoxylates, and also the corresponding reactionproducts with ammonia.

Additives comprising carboxylic ester groups (Dg) are preferably estersof mono-, di- or tricarboxylic acids with long-chain alkanols orpolyols, especially those having a minimum viscosity of 2 mm²/s at 100°C., as described more particularly in DE-A 38 38 918. The mono-, di- ortricarboxylic acids used may be aliphatic or aromatic acids, andparticularly suitable ester alcohols or ester polyols are long-chainrepresentatives having, for example, 6 to 24 carbon atoms. Typicalrepresentatives of the esters are adipates, phthalates, isophthalates,terephthalates and trimellitates of isooctanol, of isononanol, ofisodecanol and of isotridecanol. Such products also satisfy carrier oilproperties.

Additives comprising moieties derived from succinic anhydride and havinghydroxyl and/or amino and/or amido and/or especially imido groups (Dh)are preferably corresponding derivatives of alkyl- oralkenyl-substituted succinic anhydride and especially the correspondingderivatives of polyisobutenylsuccinic anhydride which are obtainable byreacting conventional or high-reactivity polyisobutene havingM_(n)=preferably 300 to 5000, more preferably 300 to 3000, even morepreferably 500 to 2500, even more especially preferably 700 to 2500 andespecially 800 to 1500, with maleic anhydride by a thermal route in anene reaction or via the chlorinated polyisobutene. The moieties havinghydroxyl and/or amino and/or amido and/or imido groups are, for example,carboxylic acid groups, acid amides of monoamines, acid amides of di- orpolyamines which, in addition to the amide function, also have freeamine groups, succinic acid derivatives having an acid and an amidefunction, carboximides with monoamines, carboximides with di- orpolyamines which, in addition to the imide function, also have freeamine groups, or diimides which are formed by the reaction of di- orpolyamines with two succinic acid derivatives. Such fuel additives arecommon knowledge and are described, for example, in documents (1) and(2). They are preferably the reaction products of alkyl- oralkenyl-substituted succinic acids or derivatives thereof with aminesand more preferably the reaction products of polyisobutenyl-substitutedsuccinic acids or derivatives thereof with amines. Of particularinterest in this context are reaction products with aliphatic polyamines(polyalkyleneimines) such as, more particularly, ethylenediamine,diethylenetriamine, triethylenetetramine, tetraethylenepentamine,pentaethylenehexamine and hexaethyleneheptamine, which have an imidestructure.

Additives comprising moieties (Di) obtained by Mannich reaction ofsubstituted phenols with aldehydes and mono- or polyamines arepreferably reaction products of polyisobutene-substituted phenols withformaldehyde and mono- or polyamines such as ethylenediamine,diethylenetriamine, triethylenetetramine, tetraethylenepentamine ordimethylaminopropylamine. The polyisobutenyl-substituted phenols mayoriginate from conventional or high-reactivity polyisobutene havingM_(n)=300 to 5000. Such “polyisobutene Mannich bases” are described moreparticularly in EP-A 831 141.

One or more of the detergent additives mentioned can be added to thefuel in such an amount that the dosage rate of these detergent additivesis preferably 25 to 2500 ppm by weight, especially 75 to 1500 ppm byweight, in particular 150 to 1000 ppm by weight.

B2) Carrier Oils

Carrier oils additionally used may be of mineral or synthetic nature.Suitable mineral carrier oils are fractions obtained in crude oilprocessing, such as brightstock or base oils having viscosities, forexample, from the SN 500-2000 class; but also aromatic hydrocarbons,paraffinic hydrocarbons and alkoxyalkanols. Likewise useful is afraction which is obtained in the refining of mineral oil and is knownas “hydrocrack oil” (vacuum distillate cut having a boiling range offrom about 360 to 500° C., obtainable from natural mineral oil which hasbeen catalytically hydrogenated under high pressure and isomerized andalso deparaffinized). Likewise suitable are mixtures of theabovementioned mineral carrier oils.

Examples of suitable synthetic carrier oils are polyolefins(polyalphaolefins or polyinternalolefins). (poly)esters,(poly)alkoxylates, polyethers, aliphatic polyether-amines,alkylphenol-started polyethers, alkylphenol-started polyetheramines andcarboxylic esters of long-chain alkanols.

Examples of suitable polyolefins are olefin polymers having M_(n)=400 to1800, in particular based on polybutene or polyisobutene (hydrogenatedor unhydrogenated).

Examples of suitable polyethers or polyetheramines are preferablycompounds comprising polyoxy-C₂- to C₄-alkylene moieties obtainable byreacting C₂- to C₆₀-alkanols. C₆- to C₃₀-alkanediols, mono- or di-C₂- toC₃₀-alkylamines, C₁- to C₃₀-alkylcycohexanols or C₁- to C₃₀-alkylphenolswith 1 to 30 mol of ethylene oxide and/or propylene oxide and/orbutylene oxide per hydroxyl group or amino group, and, in the case ofthe polyetheramines, by subsequent reductive amination with ammonia,monoamines or polyamines. Such products are described more particularlyin EP-A 310 875, EP-A 356 725, EP-A 700 985 and U.S. Pat. No. 4,877,416.For example, the polyetheramines used may be poly-C₂- to C₆-alkyleneoxide amines or functional derivatives thereof. Typical examples thereofare tridecanol butoxylates or isotridecanol butoxylates, isononylphenolbutoxylates and also polyisobutenol butoxylates and propoxylates, andalso the corresponding reaction products with ammonia.

Examples of carboxylic esters of long-chain alkanols are moreparticularly esters of mono-, di- or tricarboxylic acids with long-chainalkanols or polyols, as described more particularly in DE-A 38 38 918.The mono-, di- or tricarboxylic acids used may be aliphatic or aromaticacids; particularly suitable ester alcohols or ester polyols arelong-chain representatives having, for example, 6 to 24 carbon atoms.Typical representatives of the esters are adipates, phthalates,isophthalates, terephthalates and trimellitates of isooctanol,isononanol, isodecanol and isotridecanol, for example di(n- orisotridecyl) phthalate.

Further suitable carrier oil systems are described, for example, in DE-A38 26 608, DE-A 41 42 241, DE-A 43 09 074, EP-A 452 328 and EP-A 548617.

Examples of particularly suitable synthetic carrier oils arealcohol-started polyethers having about 5 to 35, preferably about 5 to30, more preferably 10 to 30 and especially 15 to 30 C₃- to C₆-alkyleneoxide units, for example propylene oxide, n-butylene oxide andisobutylene oxide units, or mixtures thereof, per alcohol molecule.Nonlimiting examples of suitable starter alcohols are long-chainalkanols or phenols substituted by long-chain alkyl in which thelong-chain alkyl radical is especially a straight-chain or branched C₆-to C₁₈-alkyl radical. Particular examples include tridecanol andnonylphenol. Particularly preferred alcohol-started polyethers are thereaction products (polyetherification products) of monohydric aliphaticC₆- to C₁₈-alcohols with C₃- to C₆-alkylene oxides. Examples ofmonohydric aliphatic C₆-C₁₈-alcohols are hexanol, heptanol, octanol,2-ethylhexanol, nonyl alcohol, decanol, 3-propylheptanol, undecanol,dodecanol, tridecanol, tetradecanol, pentadecanol, hexadecanol,octadecanol and the constitutional and positional isomers thereof. Thealcohols can be used either in the form of the pure isomers or in theform of technical grade mixtures. A particularly preferred alcohol istridecanol. Examples of C₃- to C₆-alkylene oxides are propylene oxide,such as 1,2-propylene oxide, butylene oxide, such as 1,2-butylene oxide,2,3-butylene oxide, isobutylene oxide or tetrahydrofuran, pentyleneoxide and hexylene oxide. Particular preference among these is given toC₃ to C₄-alkylene oxides, i.e. propylene oxide such as 1,2-propyleneoxide and butylene oxide such as 1,2-butylene oxide, 2,3-butylene oxideand isobutylene oxide. Especially butylene oxide is used.

Further suitable synthetic carrier oils are alkoxylated alkylphenols, asdescribed in DE-A 10 102 913.

Particular carrier oils are synthetic carrier oils, particularpreference being given to the above-described alcohol-startedpolyethers.

The carrier oil or the mixture of different carrier oils is added to thefuel in an amount of preferably 1 to 1000 ppm by weight, more preferablyof 10 to 500 ppm by weight and especially of 20 to 100 ppm by weight.

B3) Cold Flow Improvers

Suitable cold flow improvers are in principle all organic compoundswhich are capable of improving the flow performance of middle distillatefuels or diesel fuels under cold conditions. For the intended purpose,they must have sufficient oil solubility. More particularly, useful coldflow improvers for this purpose are the cold flow improvers (middledistillate flow improvers, MDFIs) typically used in the case of middledistillates of fossil origin, i.e. In the case of customary mineraldiesel fuels. However, it is also possible to use organic compoundswhich partly or predominantly have the properties of a wax antisettlingadditive (WASA) when used in customary diesel fuels. They can also actpartly or predominantly as nucleators. It is also possible to usemixtures of organic compounds effective as MDFIs and/or effective asWASAs and/or effective as nucleators.

The cold flow improver is typically selected from:

-   (K1) copolymers of a C₂- to C₄₀-olefin with at least one further    ethylenically unsaturated monomer.-   (K2) comb polymers.-   (K3) polyoxyalkylenes;-   (K4) polar nitrogen compounds;-   (K5) sulfocarboxylic acids or sulfonic acids or derivatives thereof;    and-   (K6) poly(meth)acrylic esters.

It is possible to use either mixtures of different representatives fromone of the particular classes (K1) to (K6) or mixtures ofrepresentatives from different classes (K1) to (K6).

Suitable C₂- to C₄₀-olefin monomers for the copolymers of class (K1)are, for example, those having 2 to 20 and especially 2 to 10 carbonatoms, and 1 to 3 and preferably 1 or 2 carbon-carbon double bonds,especially having one carbon-carbon double bond. In the latter case, thecarbon-carbon double bond may be arranged either terminally (α-olefins)or internally. However, preference is given to α-olefins, particularpreference to α-olefins having 2 to 6 carbon atoms, for example propene,1-butene, 1-pentene, 1-hexene and in particular ethylene.

In the copolymers of class (K1), the at least one further ethylenicallyunsaturated monomer is preferably selected from alkenyl carboxylates,(meth)acrylic esters and further olefins.

When further olefins are also copolymerized, they are preferably higherin molecular weight than the abovementioned C₂- to C₄₀-olefin basemonomers. When, for example, the olefin base monomer used is ethylene orpropene, suitable further olefins are especially C₁₀- to C₄₀-α-olefins.Further olefins are in most cases only additionally copolymerized whenmonomers with carboxylic ester functions are also used.

Suitable (meth)acrylic esters are, for example, esters of (meth)acrylicacid with C₁- to C₂₀-alkanols, especially C₁- to C₁₀-alkanols, inparticular with methanol, ethanol, propanol, isopropanol, n-butanol,sec-butanol, isobutanol, tert-butanol, pentanol, hexanol, heptanol,octanol, 2-ethylhexanol, nonanol and decanol, and structural isomersthereof.

Suitable alkenyl carboxylates are, for example, C₂- to C₁₄-alkenylesters, for example the vinyl and propenyl esters, of carboxylic acidshaving 2 to 21 carbon atoms, whose hydrocarbyl radical may be linear orbranched. Among these, preference is given to the vinyl esters. Amongthe carboxylic acids with a branched hydrocarbyl radical, preference isgiven to those whose branch is in the α position to the carboxyl group,and the α-carbon atom is more preferably tertiary, i.e. the carboxylicacid is what is called a neocarboxylic acid. However, the hydrocarbylradical of the carboxylic acid is preferably linear.

Examples of suitable alkenyl carboxylates are vinyl acetate, vinylpropionate, vinyl butyrate, vinyl 2-ethylhexanoate, vinyl neopentanoate,vinyl hexanoate, vinyl neononanoate, vinyl neodecanoate and thecorresponding propenyl esters, preference being given to the vinylesters. A particularly preferred alkenyl carboxylate is vinyl acetate;typical copolymers of group (K1) resulting therefrom are ethylene-vinylacetate copolymers (“EVAs”), which are some of the most frequently used.

Ethylene-vinyl acetate copolymers usable particularly advantageously andthe preparation thereof are described in WO 99/29748.

Suitable copolymers of class (K1) are also those which comprise two ormore different alkenyl carboxylates in copolymerized form, which differin the alkenyl function and/or in the carboxylic acid group. Likewisesuitable are copolymers which, as well as the alkenyl carboxylate(s),comprise at least one olefin and/or at least one (meth)acrylic ester incopolymerized form.

Terpolymers of a C₂ to C₄₀-α-olefin, a C₁- to C₂₀-alkyl ester of anethylenically unsaturated monocarboxylic acid having 3 to 15 carbonatoms and a C₂ to C₁₄-alkenyl ester of a saturated monocarboxylic acidhaving 2 to 21 carbon atoms are also suitable as copolymers of class(K1). Terpolymers of this kind are described in WO 20051054314. Atypical terpolymer of this kind is formed from ethylene, 2-ethylhexylacrylate and vinyl acetate.

The at least one or the further ethylenically unsaturated monomer(s) arecopolymerized in the copolymers of class (K1) in an amount of preferably1 to 50% by weight, especially 10 to 45% by weight and in particular 20to 40% by weight, based on the overall copolymer. The main proportion interms of weight of the monomer units in the copolymers of class (K1)therefore originates generally from the C₂- to C₄₀ base olefins.

The copolymers of class (K1) preferably have a number-average molecularweight M_(n) of 1000 to 20 000, more preferably of 1000 to 10 000 andespecially of 1000 to 8000.

Typical comb polymers of component (K2) are, for example, obtainable bythe copolymerization of maleic anhydride or fumaric acid with anotherethylenically unsaturated monomer, for example with an α-olefin or anunsaturated ester, such as vinyl acetate, and subsequent esterificationof the anhydride or acid function with an alcohol having at least 10carbon atoms. Further suitable comb polymers are copolymers of α-olefinsand esterified comonomers, for example esterified copolymers of styreneand maleic anhydride or esterified copolymers of styrene and fumaricacid. Suitable comb polymers may also be polyfumarates or polymaleates.Homo- and copolymers of vinyl ethers are also suitable comb polymers.Comb polymers suitable as components of class (K2) are, for example,also those described in WO 2004/035715 and in “Comb-Like Polymers,Structure and Properties”, N. A. Platé and V. P. Shibaev, J. Poly. Sci.Macromolecular Revs. 8, pages 117 to 253 (1974). Mixtures of combpolymers are also suitable.

Polyoxyalkylenes suitable as components of class (K3) are, for example,polyoxyalkylene esters, polyoxyalkylene ethers, mixed polyoxyalkyleneester/ethers and mixtures thereof. These polyoxyalkylene compoundspreferably comprise at least one linear alkyl group, preferably at leasttwo linear alkyl groups, each having 10 to 30 carbon atoms and apolyoxyalkylene group having a number-average molecular weight of up to5000. Such polyoxyalkylene compounds are described, for example, in EP-A061 895 and also in U.S. Pat. No. 4,491,455. Particular polyoxyalkylenecompounds are based on polyethylene glycols and polypropylene glycolshaving a number-average molecular weight of 100 to 5000. Additionallysuitable are polyoxyalkylene mono- and diesters of fatty acids having 10to 30 carbon atoms, such as stearic acid or behenic acid.

Polar nitrogen compounds suitable as components of class (K4) may beeither ionic or nonionic and preferably have at least one substituent,especially at least two substituents, in the form of a tertiary nitrogenatom of the general formula >NR⁷ in which R⁷ is a C₈- to C₄₀-hydrocarbylradical. The nitrogen substituents may also be quaternized, i.e. be incationic form. Examples of such nitrogen compounds are ammonium saltsand/or amides which are obtainable by the reaction of at least one aminesubstituted by at least one hydrocarbyl radical with a carboxylic acidhaving 1 to 4 carboxyl groups or with a suitable derivative thereof. Theamines preferably comprise at least one linear C₈- to C₄₀-alkyl radical.Primary amines suitable for preparing the polar nitrogen compoundsmentioned are, for example, octylamine, nonylamine, decylamine,undecylamine, dodecylamine, tetradecylamine and the higher linearhomologs; secondary amines suitable for this purpose are, for example,dioctadecylamine and methylbehenylamine. Also suitable for this purposeare amine mixtures, especially amine mixtures obtainable on theindustrial scale, such as fatty amines or hydrogenated tallamines, asdescribed, for example, in Ullmann's Encyclopedia of IndustrialChemistry. 6th Edition, “Amines, aliphatic” chapter. Acids suitable forthe reaction are, for example, cyclohexane-1,2-dicarboxylic acid,cydohexene-1,2-dicarboxylic acid, cyclopentane-1,2-dicarboxylic acid,naphthalenedicarboxylic acid, phthalic acid, isophthalic acid,terephthalic acid, and succinic acids substituted by long-chainhydrocarbyl radicals.

More particularly, the component of class (K4) is an oil-solublereaction product of poly(C₂- to C₂₀-carboxylic acids) having at leastone tertiary amino group with primary or secondary amines. The poly(C₂-to C₂₀-carboxylic acids) which have at least one tertiary amino groupand form the basis of this reaction product comprise preferably at least3 carboxyl groups, especially 3 to 12 and in particular 3 to 5 carboxylgroups. The carboxylic acid units in the polycarboxylic acids havepreferably 2 to 10 carbon atoms, and are especially acetic acid units.The carboxylic add units are suitably bonded to the polycarboxylic adds,usually via one or more carbon and/or nitrogen atoms. They arepreferably attached to tertiary nitrogen atoms which, in the case of aplurality of nitrogen atoms, are bonded via hydrocarbon chains.

The component of class (K4) is preferably an oil-soluble reactionproduct based on poly(C₂- to C₂₀-carboxylic acids) which have at leastone tertiary amino group and are of the general formula IIa or IIb

in which the variable A is a straight-chain or branched C₂- toC₆-alkylene group or the moiety of the formula III

and the variable B is a C₁- to C₁₉-alkylene group. The compounds of thegeneral formulae IIa and IIb especially have the properties of a WASA.

Moreover, the preferred oil-soluble reaction product of component (K4),especially that of the general formula IIa or lib, is an amide, anamide-ammonium salt or an ammonium salt in which no, one or morecarboxylic acid groups have been converted to amide groups.

Straight-chain or branched C₂- to C₆-alkylene groups of the variable Aare, for example, 1,1-ethylene, 1,2-propylene, 1,3-propylene,1,2-butylene, 1,3-butylene, 1,4-butylene, 2-methyl-1,3-propylene,1,5-pentylene, 2-methyl-1,4-butylene, 2,2-dimethyl-1,3-propylene,1,6-hexylene (hexamethylene) and especially 1,2-ethylene. The variable Acomprises preferably 2 to 4 and especially 2 or 3 carbon atoms.

C₁- to C₁₉-alkylene groups of the variable B are, for example,1,2-ethylene, 1,3-propylene, 1,4-butylene, hexamethylene, octamethylene,decamethylene, dodecamethylene, tetradecamethylene, hexadecamethylene,octadecamethylene, nonadecamethylene and especially methylene. Thevariable B comprises preferably 1 to 10 and especially 1 to 4 carbonatoms.

The primary and secondary amines as a reaction partner for thepolycarboxylic acids to form component (K4) are typically monoamines,especially aliphatic monoamines. These primary and secondary amines maybe selected from a multitude of amines which bear hydrocarbyl radicalswhich may optionally be bonded to one another.

These parent amines of the oil-soluble reaction products of component(K4) are usually secondary amines and have the general formula HN(R⁶)₂in which the two variables R⁸ are each independently straight-chain orbranched C₁₀- to C₃₀-alkyl radicals, especially C₁₄- to C₂₄-alkylradicals. These relatively long-chain alkyl radicals are preferablystraight-chain or only slightly branched. In general, the secondaryamines mentioned, with regard to their relatively long-chain alkylradicals, derive from naturally occurring fatty acids and fromderivatives thereof. The two R⁸ radicals are preferably identical.

The secondary amines mentioned may be bonded to the polycarboxylic acidsby means of amide structures or in the form of the ammonium salts; it isalso possible for only a portion to be present as amide structures andanother portion as ammonium salts. Preferably only few, if any, freeacid groups are present. The oil-soluble reaction products of component(K4) are preferably present completely in the form of the amidestructures.

Typical examples of such components (K4) are reaction products ofnitrilotriacetic acid, of ethylenediaminetetraacetic acid or ofpropylene-1,2-diaminetetraacetic acid with in each case 0.5 to 1.5 molper carboxyl group, especially 0.8 to 1.2 mol per carboxyl group, ofdioleylamine, dipalmitamine, dicocoamine, distearylamine, dibehenylamineor especially ditallamine. A particularly preferred component (K4) isthe reaction product of 1 mol of ethylenediaminetetraacetic acid and 4mol of hydrogenated ditallamine.

Further typical examples of component (K4) include theN,N-dialkylammonium salts of 2-N′,N′-dialkylamidobenzoates, for examplethe reaction product of 1 mol of phthalic anhydride and 2 mol ofditallamine, the latter being hydrogenated or unhydrogenated, and thereaction product of 1 mol of an alkenylspirobislactone with 2 mol of adialkylamine, for example ditallamine and/or tallamine, the latter twobeing hydrogenated or unhydrogenated.

Further typical structure types for the component of class (K4) arecyclic compounds with tertiary amino groups or condensates of long-chainprimary or secondary amines with carboxylic acid-containing polymers, asdescribed in WO 93/18115.

Sulfocarboxylic acids, sulfonic acids or derivatives thereof which aresuitable as cold flow improvers of the component of class (K5) are, forexample, the oil-soluble carboxamides and carboxylic esters ofortho-sulfobenzoic acid, in which the sulfonic acid function is presentas a sulfonate with alkyl-substituted ammonium cations, as described inEP-A 261 957.

Poly(meth)acrylic esters suitable as cold flow improvers of thecomponent of class (K6) are either homo- or copolymers of acrylic andmethacrylic esters. Preference is given to copolymers of at least twodifferent (meth)acrylic esters which differ with regard to theesterified alcohol. The copolymer optionally comprises another differentolefinically unsaturated monomer in copolymerized form. Theweight-average molecular weight of the polymer is preferably 50 000 to500 000. A particularly preferred polymer is a copolymer of methacrylicacid and methacrylic esters of saturated C₁₄- and C₁₅-alcohols, the acidgroups having been neutralized with hydrogenated tallamine. Suitablepoly(meth)acrylic esters are described, for example, in WO 00/44857.

The cold flow improver or the mixture of different cold flow improversis added to the middle distillate fuel or diesel fuel in a total amountof preferably 10 to 5000 ppm by weight, more preferably of 20 to 2000ppm by weight, even more preferably of 50 to 1000 ppm by weight andespecially of 100 to 700 ppm by weight, for example of 200 to 500 ppm byweight.

B4) Lubricity Improvers

Suitable lubricity improvers or friction modifiers are based typicallyon fatty acids or fatty acid esters. Typical examples are tall oil fattyacid, as described, for example, in WO 98/004656, and glycerylmonooleate. The reaction products, described in U.S. Pat. No. 6,743,266B2, of natural or synthetic oils, for example triglycerides, andalkanolamines are also suitable as such lubricity improvers.

B5) Corrosion Inhibitors Other than the Copolymer Described

Suitable corrosion inhibitors are, for example, succinic esters, inparticular with polyols, fatty acid derivatives, for example oleicesters, oligomerized fatty acids, substituted ethanolamines, andproducts sold under the trade name RC 4801 (Rhein Chemie Mannheim,Germany), Irgacor® L12 (BASF SE) or HiTEC 536 (Ethyl Corporation).

B6) Demulsifiers

Suitable demulsifiers are, for example, the alkali metal or alkalineearth metal salts of alkyl-substituted phenol- and naphthalenesulfonatesand the alkali metal or alkaline earth metal salts of fatty acids, andalso neutral compounds such as alcohol alkoxylates, e.g. alcoholethoxylates, phenol alkoxylates, e.g. tert-butylphenol ethoxylate ortert-pentylphenol ethoxylate, fatty acids, alkylphenols, condensationproducts of ethylene oxide (EO) and propylene oxide (PO), for exampleincluding in the form of EO/PO block copolymers, polyethyleneimines orelse polysiloxanes.

B7) Dehazers

Suitable dehazers are, for example, alkoxylated phenol-formaldehydecondensates, for example the products available under the trade namesNALCO 7D07 (Nalco) and TOLAD 2683 (Petrolite).

B8) Antifoams

Suitable antifoams are, for example, polyether-modified polysiloxanes,for example the products available under the trade names TEGOPREN 5851(Goldschmidt), Q 25907 (Dow Corning) and RHODOSIL (Rhone Poulenc).

B9) Cetane Number Improvers

Suitable cetane number improvers are, for example, aliphatic nitratessuch as 2-ethylhexyl nitrate and cyclohexyl nitrate and peroxides suchas di-tert-butyl peroxide.

B10) Antioxidants

Suitable antioxidants are, for example substituted phenols, such as2,6-di-tert-butylphenol and 6-di-tert-butyl-3-methylphenol, and alsophenylenediamines such as N,N′-di-sec-butyl-p-phenylenediamine.

B11) Metal Deactivators

Suitable metal deactivators are, for example, salicylic acid derivativessuch as N,N′-disalicylidene-1,2-propanediamine.

B12) Solvents

Suitable solvents are, for example, nonpolar organic solvents such asaromatic and aliphatic hydrocarbons, for example toluene, xylenes, whitespirit and products sold under the trade names SHELLSOL (RoyalDutch/Shell Group) and EXXSOL (ExxonMobil), and also polar organicsolvents, for example, alcohols such as 2-ethythexanol, decanol andisotridecanol. Such solvents are usually added to the diesel fueltogether with the aforementioned additives and coadditives, which theyare intended to dissolve or dilute for better handling.

C) Fuels

The inventive use relates in principle to any fuels, preferably dieselfuels and gasoline fuels.

Middle distillate fuels such as diesel fuels or heating oils arepreferably mineral oil raffinates which typically have a boiling rangefrom 100 to 400° C. These are usually distillates having a 95% point upto 360° C. or even higher. These may also be what is called “ultra lowsulfur diesel” or “city diesel”, characterized by a 95% point of, forexample, not more than 345° C. and a sulfur content of not more than0.005% by weight or by a 95% point of, for example, 285° C. and a sulfurcontent of not more than 0.001% by weight. In addition to the mineralmiddle distillate fuels or diesel fuels obtainable by refining, thoseobtainable by coal gasification or gas liquefaction [“gas to liquid”(GTL) fuels] or by biomass liquefaction [“biomass to liquid” (BTL)fuels] are also suitable. Also suitable are mixtures of theaforementioned middle distillate fuels or diesel fuels with renewablefuels, such as biodiesel or bioethanol.

The qualities of the heating oils and diesel fuels are laid down indetail, for example, in DIN 51603 and EN 590 (cf. also Ullmann'sEncyclopedia of Industrial Chemistry, 5th edition, Volume A12, p. 617ff.).

The inventive use in middle distillate fuels of fossil, vegetable oranimal origin, which are essentially hydrocarbon mixtures, also relatesto mixtures of such middle distillates with biofuel oils (biodiesel).Mixtures of this kind are encompassed by the term “middle distillatefuel”. They are commercially available and usually comprise the biofueloils in minor amounts, typically in amounts of 1 to 30% by weight,especially of 3 to 10% by weight, based on the total amount of middledistillate of fossil, vegetable or animal origin and biofuel oil.

Biofuel oils are generally based on fatty acid esters, preferablyessentially on alkyl esters of fatty acids which derive from vegetableand/or animal oils and/or fats. Alkyl esters are typically understood tomean lower alkyl esters, especially C₁- to C₄-alkyl esters, which areobtainable by transesterifying the glycerides which occur in vegetableand/or animal oils and/or fats, especially triglycerides, by means oflower alcohols, for example ethanol or in particular methanol (“FAME”).Typical lower alkyl esters based on vegetable and/or animal oils and/orfats, which find use as a biofuel oil or components thereof, are, forexample, sunflower methyl ester, palm oil methyl ester (“PME”), soya oilmethyl ester (“SME”) and especially rapeseed oil methyl ester (“RME”).

The middle distillate fuels or diesel fuels are more preferably thosehaving a low sulfur content, i.e. having a sulfur content of less than0.05% by weight, preferably of less than 0.02% by weight, moreparticularly of less than 0.005% by weight and especially of less than0.001% by weight of sulfur.

Useful gasoline fuels include all commercial gasoline fuel compositions.One typical representative which shall be mentioned here is theEurosuper base fuel to EN 228, which is customary on the market. Inaddition, gasoline fuel compositions of the specification according toWO 00/47698 are also possible fields of use for the present invention.

The examples which follow are intended to illustrate the presentinvention, without restricting it.

EXAMPLES GPC Analysis

Unless stated otherwise, the mass-average molecular weight Mw andnumber-average molecular weight Mn of the polymers was measured by meansof gel permeation chromatography (GPC). GPC separation was effected bymeans of two PLge Mixed B columns (Agilent) In tetrahydrofuran at 35° C.Calibration was effected by means of a narrow-distribution polystyrenestandard (from PSS, Germany) having a molecular weight of 162-50 400 Da.Hexylbenzene was used as a marker for low molecular weight.

PREPARATION EXAMPLES General Procedure

A reactor having an anchor stirrer was initially charged with the olefinor the mixture of olefins with or without solvent (as a bulkpolymerization). The mixture was heated to the temperature specifiedunder a nitrogen stream and while stirring. To this were added thefree-radical initiator specified (optionally diluted in the samesolvent) and molten maleic anhydride (1 equivalent based on olefinmonomer). The reaction mixture was stirred at the same temperature forthe reaction time specified and then cooled down.

If hydrolysis is desired, water was subsequently added in the amountspecified and the mixture was stirred either at 95° C. for 10-14 h orunder pressure at 110° C. for 3 h.

Synthesis Example 1

A 2 L glass reactor having an anchor stirrer was initially charged witha mixture of C₂₀-C₂₄ olefins (363.2 g, average molar mass 296 g/mol) andSolvesso 150 (231.5 g, DHC Solvent Chemie GmbH, Speldorf). The mixturewas heated to 160° C. in a nitrogen stream and while stirring. To thiswere added, within 5 h, a solution of di-tert-butyl peroxide (29.6 g,from Akzo Nobel) in Solvesso 150 (260.5 g) and molten maleic anhydride(120.3 g). The reaction mixture was stirred at 160° C. for 1 h and thencooled down. The active ingredient content was about 40%.

GPC (in THF) gave an Mn=1210 g/mol, Mw=2330 g/mol for the copolymer,which corresponds to a polydispersity of 1.9.

Synthesis Example 2 (Comparison)

Water (19.9 g) was added to the product from synthesis example 1 at atemperature of 95° C. within 3 h and the mixture was then stirred for afurther 11 h. The acid number was 104 mg KOH/g

USE EXAMPLES 1) Calcium Compatibility Test:

100 mL of motor oil (Shell Helix®, FIG. 1, far left beaker, with a Cacontent of 1500 ppm, Mg content of 1100 ppm and Zn content of 1300 ppm)were heated to 70° C. in the beaker and then 1 mL of corrosion Inhibitorwas added (top of FIG. 1). Should the solution still be clear, a further1 mL of inhibitor is added (bottom of FIG. 1). If the solution turnscloudy, the test is considered to have been failed (e.g. FIG. 1, middlebeaker). FIG. 1 shows the oil which has been admixed with copolymeraccording to synthesis example 1 (40% in solvent naphtha) and remainsclear. In the middle beaker, dimer fatty acid (dimeric oleic acid; CAS:61788-89-4, 20% in solvent naphtha) was used. Clearly visible cloudinessis apparent.

The above synthesis examples were used to produce, by mixing withpolyisobutenamine (molar mass 1000), polypropylene glycol as carrier oiland solvent and dehazer, the following adhesive formulations which wereused in the use examples (compositions in parts by weight):

Figures in Carrier Solvent/ mg/kg Polyisobutenamine oil dehazerAnticorrosive Formulation 1 248 195 47 10 (comparative) (dimer fattyacid) Formulation 2 248 195 47 10 (comparative) (synthesis example 2)Formulation 3 248 195 47 10 (synthesis example 1)2) Steel Corrosion Test in Accordance with ASTM D 665 B (Gasoline)

The fuel used was commercial EO CEC RF-12-09 gasoline fuel fromHaltermann, additized with an additive package composed ofpolyisobutenamine and carrier oil as specified above. Added to theformulation were the corrosion inhibitors specified in the table thatfollows (each 40% in solvent naphtha), and they were subjected to acorrosion test in accordance with ASTM D 665 B.

The comparison used was dimer fatty acid as corrosion inhibitor (dimericoleic acid; CAS: 61788-89-4, 40% in solvent naphtha).

Formulation Dosage [mg/kg] Anticorrosive NACE rating Haltermann E0unadditized fuel — D CEC RF-12-09 Formulation 1 500 10 mg/kg dimer B++(comparative) fatty acid Formulation 2 500 10 mg/kg synthesis B++(comparative) example 2 Formulation 3 500 10 mg/kg synthesis B+ example1

The assessment was made as follows:

A 100% rust-freeB++ 0.1% or less of the total surface area rustedB+ 0.1% to 5% of the total surface area rustedB 5% to 25% of the total surface area rustedC 25% to 50% of the total surface area rustedD 50% to 75% of the total surface area rustedE 75% to 100% of the total surface area rusted

It can be seen that similarly good results are achieved with thecopolymer of the invention as with the comparative compounds.

3) Steel Corrosion Test in Accordance with ASTM D 665 B (Diesel)

The fuel used was commercial diesel fuel from South America which wasadmixed with an additive package as follows:

Figures in Detergent/antifoam/ mg/kg solvent/dehazer AnticorrosiveFormulation 5 96 5 (comparative) (comparative) Formulation 6 96 12.5(synthesis example 1)

The anticorrosive from formulation 5 as comparison is2-(8-heptadecen-1-yl)-4,5-dihydro-1H-imidazol-1-ethanol, CAS No.95-38-5, active ingredient content 90-100%.

In formulation 6 of the invention, the product from synthesis example 1(40% in Solvesso 150) was used.

The formulations specified in the following table were subjected to acorrosion test in accordance with ASTM D 665 B:

NACE Formulation Dosage [mg/kg] Anticorrosive rating Formulation 4Unadditized test — E fuel from South America Formulation 5 1012-(8-Heptadecen-1-yl)- C (comparative) 4,5-dihydro-1H-imidazol-1-ethanol Formulation 6 108.5 Synthesis example 1 C

It can be seen that similarly good results are achieved with thecopolymer of the invention as with the comparative compound.

1: A process, comprising inhibiting corrosion in a fuel or lubricant bycontacting the fuel or lubricant with a copolymer, wherein the copolymeris obtained by: (I) copolymerizing (A) at least one ethylenicallyunsaturated mono- or dicarboxylic acid or derivatives thereof, (B) atleast one α-olefin having from at least 12 up to and including 30 carbonatoms, (C) optionally at least one further aliphatic or cycloaliphaticolefin which has at least 4 carbon atoms and is different than (B), and(D) optionally one or more further copolymerizable monomers other thanmonomers (A), (B) and (C), selected from the group consisting of (Da)vinyl esters, (Db) vinyl ethers, (Dc) (meth)acrylic esters of alcoholshaving at least 5 carbon atoms, (Dd) allyl alcohols or ethers thereof,(De) N-vinyl compounds selected from the group consisting of vinylcompounds of heterocycles containing at least one nitrogen atom,N-vinylamides or N-vinyllactams, (Df) ethylenically unsaturatedaromatics, (Dg) α,β-ethylenically unsaturated nitriles, (Dh)(meth)acrylamides and (Di) allylamines, to obtain a copolymer precursor;and then (II) optionally partly hydrolyzing anhydride functionalities,carboxylic ester functionalities, or both, present in the copolymerprecursor, with the proviso that more than 90% of the anhydride andcarboxylic ester functionalities present remain intact after thehydrolyzing, to obtain the copolymer. 2: The process of claim 1,comprising contacting the copolymer with a fuel comprising at least onemetal selected from the group consisting of sodium, zinc, magnesium andcalcium. 3: The process of claim 1, wherein monomer (A) is selected fromthe group consisting of acrylic acid, methacrylic acid, methyl acrylate,ethyl acrylate, n-butyl acrylate, methyl methacrylate and maleicanhydride. 4: The process of claim 1, wherein monomer (B) is an α-olefinhaving from 14 to 26 carbon atoms. 5: The process of claim 1, whereinolefin (C) is a polymer having more than 30 carbon atoms derived fromunits of propene, 1-butene, 2-butene, isobutene, or mixtures thereof,and having an average molecular weight Mw ranging from 500 to 5000g/mol. 6: The process of claim 1, wherein a mixture of olefins (B) and(C) averaged to molar amounts thereof has at least 12 carbon atoms. 7:The process of claim 1, wherein the copolymerizing (I) includes amonomer (D) selected from the group consisting of (Da), (Db), (Dc), (De)and (Df). 8: The process of claim 1, wherein a molar ratio of (A)/((B)and (C)) (in total) is from 10:1 to 1:10. 9: The process of claim 8,wherein the molar ratio of monomer (B) to monomer (C) is from 1:0.05 to10. 10: The process of claim 8, wherein a proportion of the one or morefurther copolymerizable monomers (D), based on an amount of the monomers(A), (B) and optionally (C) (in total), is 5 to 200 mol %. 11: Theprocess of claim 1, wherein maleic anhydride is used as component (A)and the optional reaction step (II) is not conducted. 12: The process ofclaim 1, wherein maleic anhydride is used as component (A) and more than90% and up to 99.9% of the anhydride functionalities remain intact inreaction step (II). 13: The process of claim 1, wherein the inhibitingcorrosion involves inhibiting corrosion of at least one iron surface,steel surface, nonferrous metal surface, or combination thereof. 14: Theprocess of claim 1, wherein the inhibiting corrosion involves inhibitingcorrosion of copper and copper-containing alloys. 15: The process ofclaim 1, wherein the fuel is a diesel or gasoline fuel.